Transition metals induce control of enhanced NLO properties of functionalized organometallic complexes under laser modulations

S. Taboukhat,N. Kichou,K. Waszkowska,J.-L. Fillaut,A. Migalska-Zalas,B. Sahraoui,A. Zawadzka,O. Alévêque,A. El-Ghayoury

doi:10.1038/s41598-020-71769-2

Abstract

The molecular engineering of organometallic complexes has recently attracted renewed interest on account of their potential technological applications for optoelectronics in general and optical data storage. The transition metal which induces control of enhanced nonlinear optical properties of functionalized organometallic complexes versus not only the intensity but also the polarization of the incident laser beam is original and important for all optical switching. This makes organometallic complexes valuable and suitable candidates for nonlinear optical applications. In the present work, we report the synthesis and full characterization of four organometallic complexes consisting of N, N-dibutylamine and azobenzene fragments but differ by auxiliary alkynyl ligands or metal cations. Thus, a ferrocenyl derivative 1 and three ruthenium complexes 2–4 have been prepared. The nonlinear optical properties of the four new azo-based ruthenium and iron organometallic complexes in the solid state, using polymethylmethacrylate as matrix, have been thoroughly studied. This concept is extended to computing the HOMO and LUMO energy levels of the considered complexes, dipole moment, first and second order hyperpolarizabilities using the 6–31 + G(d,p) + LANL2DZ mixed basis set. The second and third nonlinear optical properties of the resulting polymer composites were obtained by measuring SHG and THG response by means of the Maker fringe technique using a laser generating at 1,064 nm with a 30 ps pulse duration. The values of the second and third order NLO susceptibilities of the four organometallic complexes were found to be higher than the common references used. Theoretical calculation shows that the large first and second order hyperpolarizablities are caused by strong intramolecular charge transfer between the transition metal parts and the ligands though a conjugated transmitter. These results indicate that the present organometallic complexes are valuable candidates for optoelectronic and photonic applications.

Highlights

The molecular engineering of organometallic complexes has recently attracted renewed interest on account of their potential technological applications for optoelectronics in general and optical data storage
The synthesis of the ruthenium acetylide derivatives 2–4 was attempted by the activation of the azo-containing alkyne 6 (E)-N,N-dibutyl-4-((4-ethynylphenyl)diazenyl)aniline[21,37], in a two-steps procedure, via the formation of vinylidene intermediates (Fig. 3) followed by deprotonation, as was shown to occur for RuCl2(dppe)2 analogues[21,37]
The UV–vis spectra for the alkynyl-metal complex 4 shows a broad absorption band from 380 to 550 nm, that would correspond to the superimposition of both a metal-to-ligand charge transfer (MLCT) band around 400 nm, that is concordant with the data mentioned for other Ru(-C⋮C-R) (PPh3)2(η5-C5H5) (R = H, CHO) c omplexes[52], and the π–π* absorption bands of the azobenzene chromophore, as observed in the previous compounds

Summary

Introduction

The molecular engineering of organometallic complexes has recently attracted renewed interest on account of their potential technological applications for optoelectronics in general and optical data storage. The nonlinear optical (NLO) responses of these complexes, related to metal acetylide complexes, have been evaluated by means of second and third harmonic generations (SHG, THG) experimental techniques and quantum chemical calculations. The relations between theoretically calculated NLO properties and the experimental obtained second and third order susceptibilities are presented.

Results

Conclusion